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The Journal of Neuroscience, March 15, 2003, 23(6):2093
Novel Isoforms of Dlg Are Fundamental for Neuronal Development in
Drosophila
Carolina
Mendoza1,
Patricio
Olguín1,
Gabriela
Lafferte1,
Ulrich
Thomas2,
Susanne
Ebitsch2,
Eckart D.
Gundelfinger2,
Manuel
Kukuljan1, and
Jimena
Sierralta1
1 Programa de Fisiología y Biofísica,
Instituto de Ciencias Biomédicas, Facultad de Medicina,
Universidad de Chile, Santiago, Chile 6530499, and
2 Leibniz Institute for Neurobiology, D-39118 Magdeburg,
Germany
Drosophila discs-large (dlg)
mutants exhibit multiple developmental abnormalities, including severe
defects in neuronal differentiation and synaptic structure and
function. These defects have been ascribed to the loss of a single gene
product, Dlg-A, a scaffold protein thought to be expressed in many cell
types. Here, we describe that additional isoforms arise as a
consequence of different transcription start points and alternative
splicing of dlg. At least five different dlg gene products are predicted. We identified a subset
of dlg-derived cDNAs that include novel exons encoding a
peptide homologous to the N terminus of the mammalian protein
SAP97/hDLG (S97N). Dlg isoforms containing the S97N domain are
expressed at larval neuromuscular junctions and within the CNS of both
embryos and larvae but are not detectable in epithelial tissues. Strong
hypomorphic dlg alleles exhibit decreased expression of
S97N, which may account for neural-specific aspects of the pleiomorphic
dlg mutant phenotype. Selective inhibition of the
expression of S97N-containing proteins in embryos by double-strand RNA
leads to severe defects in neuronal differentiation and axon guidance,
without overt perturbations in epithelia. These results indicate that
the differential expression of dlg products correlates with distinct functions in non-neural and neural cells. During embryonic development, proteins that include the S97N domain are essential for proper neuronal differentiation and organization, acting
through mechanisms that may include the adequate localization of cell
fate determinants.
Key words:
dlg; SAP97; alternative transcripts; neuronal differentiation; scaffold proteins; dsRNA; Drosophila
Copyright © 2003 Society for Neuroscience 0270-6474/03/2362093-09$05.00/0
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